The Collaborative International Dictionary of English v.0.48:

Baptize \Bap*tize"\, v. t. [imp. & p. p. Baptized; p. pr. &
   vb. n. Baptizing.] [F. baptiser, L. baptizare, fr. Gr.
   bapti`zein. See Baptism.]
   1. To administer the sacrament of baptism to.
      [1913 Webster]

   2. To christen (because a name is given to infants at their
      baptism); to give a name to; to name.
      [1913 Webster]

            I'll be new baptized;
            Henceforth I never will be Romeo.     --Shak.
      [1913 Webster]

   3. To sanctify; to consecrate.
      [1913 Webster]

WordNet (r) 3.0 (2006):

baptize
    v 1: administer baptism to; "The parents had the child baptized"
         [syn: baptize, baptise, christen]

Moby Thesaurus II by Grady Ward, 1.0:

83 Moby Thesaurus words for "baptize":
   adulterate, asperge, asperse, attenuate, bath, bathe, bury, call,
   christen, cleanse, cut, define, deluge, denominate, designate,
   dilute, dip, douche, douse, drown, dub, duck, dunk, engulf,
   entitle, flush, flush out, gargle, holystone, identify, immerge,
   immerse, inundate, irrigate, label, lather, launder, lave, merge,
   mop, mop up, name, nickname, nominate, overwhelm, plunge in water,
   purify, rarefy, reduce, regenerate, rinse, rinse out,
   ritually immerse, scour, scrub, scrub up, shampoo, shower, sink,
   sluice, sluice out, soap, souse, specify, sponge, sprinkle, style,
   submerge, submerse, swab, syringe, tag, term, thin, title, toivel,
   tub, wash, wash out, wash up, water, water down, whelm